一文详解Golang 定时任务库 gron 设计和原理_Golang_

$ go get github.com/roylee0704/gron

package main import ( "fmt" "time" "github.com/roylee0704/gron" ) func main() { c := gron.New() c.AddFunc(gron.Every(1*time.Hour), func() { fmt.Println("runs every hour.") }) c.Start() }

import "github.com/roylee0704/gron/xtime" gron.Every(1 * xtime.Day) gron.Every(1 * xtime.Week)

gron.Every(30 * xtime.Day).At("00:00") gron.Every(1 * xtime.Week).At("23:59")

// Cron provides a convenient interface for scheduling job such as to clean-up // database entry every month. // // Cron keeps track of any number of entries, invoking the associated func as // specified by the schedule. It may also be started, stopped and the entries // may be inspected. type Cron struct { entries []*Entry running bool add chan *Entry stop chan struct{} } // New instantiates new Cron instant c. func New() *Cron { return &Cron{ stop: make(chan struct{}), add: make(chan *Entry), } }

// Entry consists of a schedule and the job to be executed on that schedule. type Entry struct { Schedule Schedule Job Job // the next time the job will run. This is zero time if Cron has not been // started or invalid schedule. Next time.Time // the last time the job was run. This is zero time if the job has not been // run. Prev time.Time } // Schedule is the interface that wraps the basic Next method. // // Next deduces next occurring time based on t and underlying states. type Schedule interface { Next(t time.Time) time.Time } // Job is the interface that wraps the basic Run method. // // Run executes the underlying func. type Job interface { Run() }

// byTime is a handy wrapper to chronologically sort entries. type byTime []*Entry func (b byTime) Len() int { return len(b) } func (b byTime) Swap(i, j int) { b[i], b[j] = b[j], b[i] } // Less reports `earliest` time i should sort before j. // zero time is not `earliest` time. func (b byTime) Less(i, j int) bool { if b[i].Next.IsZero() { return false } if b[j].Next.IsZero() { return true } return b[i].Next.Before(b[j].Next) }

 // JobFunc is an adapter to allow the use of ordinary functions as gron.Job // If f is a function with the appropriate signature, JobFunc(f) is a handler // that calls f. // // todo: possibly func with params? maybe not needed. type JobFunc func() // Run calls j() func (j JobFunc) Run() { j() } // AddFunc registers the Job function for the given Schedule. func (c *Cron) AddFunc(s Schedule, j func()) { c.Add(s, JobFunc(j)) } // Add appends schedule, job to entries. // // if cron instant is not running, adding to entries is trivial. // otherwise, to prevent data-race, adds through channel. func (c *Cron) Add(s Schedule, j Job) { entry := &Entry{ Schedule: s, Job: j, } if !c.running { c.entries = append(c.entries, entry) return } c.add <- entry }

// Start signals cron instant c to get up and running. func (c *Cron) Start() { c.running = true go c.run() } // Stop halts cron instant c from running. func (c *Cron) Stop() { if !c.running { return } c.running = false c.stop <- struct{}{} }

 var after = time.After // run the scheduler... // // It needs to be private as it's responsible of synchronizing a critical // shared state: `running`. func (c *Cron) run() { var effective time.Time now := time.Now().Local() // to figure next trig time for entries, referenced from now for _, e := range c.entries { e.Next = e.Schedule.Next(now) } for { sort.Sort(byTime(c.entries)) if len(c.entries) > 0 { effective = c.entries[0].Next } else { effective = now.AddDate(15, 0, 0) // to prevent phantom jobs. } select { case now = <-after(effective.Sub(now)): // entries with same time gets run. for _, entry := range c.entries { if entry.Next != effective { break } entry.Prev = now entry.Next = entry.Schedule.Next(now) go entry.Job.Run() } case e := <-c.add: e.Next = e.Schedule.Next(time.Now()) c.entries = append(c.entries, e) case <-c.stop: return // terminate go-routine. } } }

gron.Every(30 * xtime.Day).At("00:00") gron.Every(1 * xtime.Week)
                
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